First of all, this invention relates to a resin composition comprising a polycarbonate and a polyolefin which exhibits an improved polycarbonate/polyolefin compatibility and improved delamination resistance and which also has sufficient mechanical strength and heat resistance. This invention also relates to a method for producing such resin composition. In the second place, this invention relates to resin compositions comprising a polycarbonate and a polyolefin which have improved wear resistant properties or an improved solvent resistance, and articles produced by melt molding such resin compositions. In the third place, this invention relates to compositions wherein the above-described resin compositions are further blended with glass fiber, and articles molded from such compositions. The materials provided by the present invention are particularly preferable for use in office automation equipment, household appliance, automobile components, medical instruments, and the like.
Polycarbonate resins have been widely used field of automobiles and electricity owing to their excellent heat resistance, impact resistance, and electric properties as well as good dimensional stability. Polycarbonate resins, however, suffer from high melt viscosity and poor organic solvent resistance as well as poor abrasion/friction properties, and their use was limited in the fields wherein such properties were required. In order to obviate such defects of the polycarbonates, various attempts have been suggested wherein the polycarbonate is mixed with a polyolefin (See for example, Japanese Patent Publication No. 40(1965)-13664 and Japanese Patent Application Laid-Open No. 59(1984)-223741). Such resin compositions, however, failed to prove practical since the low compatibility of the polycarbonate and the polyolefin resulted in delamination, and hence, in poor appearance of the product when a molded article is produced from the resin composition by such means as injection molding. Various attempts have been made to improve the compatibility of the polycarbonate and the polyolefin by incorporating into the polycarbonate-polyolefin resin composition a polystyrene-polyolefin copolymer such as SEBS (styrene-ethylene/butylene-styrene copolymer), SEP (styrene-ethylene/propylene), or the like (See for example, Japanese Patent Application Laid-Open No. 64 (1989)-75543). However, the incorporated polystyrene-polyolefin copolymer is of elastomeric nature, and the resulting resin composition suffered particularly from poor heat resistance and flexural rigidity.
Japanese Patent Application Laid-Open No. 63(1988)-215750 discloses a resin composition wherein the polycarbonate-polyolefin resin further comprises a polycarbonate having a terminal carboxyl group and a polypropylene having epoxy group; and Japanese Patent Application Laid-Open No. 63(1988)-215752 discloses a resin composition wherein the polycarbonate-polyolefin resin further comprises a polycarbonate having a terminal hydroxyl group and polypropylene having carboxyl group. Such compositions do not undergo delamination, and the articles prepared from such compositions exhibit excellent mechanical strength and organic solvent resistance as well as improved outer appearance with no delamination. However, the carboxyl- and the hydroxyl-containing polycarbonates used for constituting such resins are those respectively prepared by adding a special monomer in the polymerization stage of the polycarbonate resin, and production of such resins would require a polycarbonate polymerization installation. Therefore, processes utilizing such components would put a heavy financial burden to resin manufacturers that do not have such polycarbonate polymerization installation. Accordingly, production of the polycarbonate-polyolefin resin further comprising such resin component was rather difficult. In addition, the properties of the resin composition estimated from the value described in the disclosed specification are not fully sufficient in view of the properties inherent to the polycarbonate, and further improvements in the properties are desired.
Attempts have also been made to add a fluororesin such as polytetrafluoroethylene to the polycarbonate resin to thereby improve friction/abrasion properties. Such composition has improved wear resistant properties in addition to the above-described excellent properties inherent to the polycarbonate resin, and therefore, such composition is used for such parts as gears and cums of office automation equipment and household appliance where heat resistance, impact strength, and wear resistant properties are required. However, the fluororesin used in such composition is rather expensive, and upon thermal disposal of the resin composition, the fluororesin would generate toxic gases. In view of such situation, there has been a strong demand for a polycarbonate based resin slide material that may substitute for the polycarbonate/fluororesin based resin composition.
On the other hand, polyolefin resins, and in particular, high density polyethylene, low density polyethylene, and straight-chain low density polyethylene are inexpensive and excellent in friction/abrasion properties. Such polyolefin resins are, however, inferior to the polycarbonate resins in their heat resistance, flexural rigidity, and flame retardancy. Therefore, it has been difficult to use the polyolefin resin in the applications where the polycarbonate/fluororesin based resin composition had been used. In view of such situation, various attempts have been made to mix the polycarbonate with the polyethylene in order to develop a resin composition which is provided with both the excellent heat resistance, impact resistance, and flame retardancy of the polycarbonate resin and the excellent friction/abrasion properties of the polyethylene. In spite of such attempts, the markedly poor compatibility of the polycarbonate with the polyethylene resulted in delamination of the molded article, especially upon frictional contact or under abrasion, leading to poor abrasion properties. Accordingly, the mixing of the polycarbonate and the polyethylene by simple kneading proved insufficient.
Polycarbonate resins are amorphous, and suffer from cracks when they are brought in contact with an organic solvent for a prolonged period. Such cracks result in significantly poor appearance and markedly reduced mechanical strength. Therefore, use of the polycarbonate resins was limited in applications where organic resistance was required. In view of such situation, attempts have been made to combine the polycarbonate with a crystalline polyester such as polyethylene terephthalate and polybutylene terephthalate to thereby improve the organic solvent resistance of the polycarbonate. Such compositions exhibit good compatibility and well-balanced mechanical strength and organic solvent resistance. However, the polyethylene terephthalate and the polybutylene terephthalate used in such resins are rather expensive. Although polyolefins such as polypropylene and polyethylene are excellent in organic solvent resistance and more inexpensive than such polyesters, polyolefins suffer from poor compatibility with the polycarbonate. As described above, mixing of the polycarbonate and the polyolefin by simple kneading failed to provide the molded article whose organic solvent resistance and appearance (resistance to delamination) were fully improved. Accordingly, no means are so far available that can improve the solvent resistance of the polycarbonate resin in an inexpensive manner.
Glass fiber-reinforced polycarbonate resins comprising a polycarbonate resin and glass fibers blended therewith have improved flexural rigidity, heat resistance and abrasion properties compared to the resin composition solely comprising the polycarbonate resin. The glass fiber-reinforced polycarbonate resins, however, are still insufficient in abrasion properties, and accordingly, use of such resins was limited in the applications where friction/abrasion properties are required, for example, gear, cum, and bearing.
In view of such situation, attempts have been made to combine the glass fiber-reinforced polycarbonate resins with a fluororesin such as polytetrafluoroethylene to thereby improve the friction/abrasion properties. Such resin compositions having the fluororesin incorporated therein have improved wear resistant properties in addition to the above-described excellent properties inherent to the polycarbonate resin, and therefore, such compositions are used for such parts as gears and cums of office automation equipment and household appliance where heat resistance, impact strength, flexural rigidity, and wear resistant properties are required. However, the fluororesin used in such composition suffer from the disadvantages as described above, and there is a strong demand for a polycarbonate based resin slide material that can substitute for the glass fiber-reinforced polycarbonate/fluororesin based resin compositions.
On the other hand, polyolefin resins, and in particular, high density polyethylene, low density polyethylene, and straight-chain low density polyethylene are inexpensive and excellent in friction/abrasion properties, as described above. However, the polyolefin resins having glass fibers admixed therewith are inferior to the glass fiber-reinforced polycarbonate resins in their heat resistance, flexural rigidity, and flame retardancy. Therefore, it has been difficult to use the glass fiber-reinforced polyolefin resin in the applications where the glass fiber-reinforced polycarbonate/fluororesin based resin compositions had been used.
In view of such situation, various attempts have been made to incorporate the glass fiber into the mixture of the polycarbonate with the polyethylene in order to develop a glass fiber-reinforced polycarbonate based resin composition which is provided with both the excellent heat resistance, impact resistance, and flame retardancy of the polycarbonate resin and the excellent friction/abrasion properties of the polyethylene. As described above, the compatibility of the polycarbonate with the polyethylene is quite poor, and the article molded from the resin composition prepared by simple kneading of the components suffered from delamination, especially upon frictional contact or under abrasion, leading to poor abrasion properties. Such situation is not at all improved by mere incorporation of the glass fiber into the resin composition.
First object of the present invention is to provide a polycarbonate/polyolefin based resin composition which is provided with the excellent mechanical properties of the polycarbonate and the excellent molding properties of the polyolefin, and which is excellent in surface properties without suffering from delamination; and to enable the production of such polycarbonate/polyolefin based resin composition by blending readily available starting materials in a convenient manner.
Second object of the present invention is to provide a method for producing such polycarbonate/polyolefin based resin composition wherein a simple kneading machine may be utilized in the production.
Third object of the present invention is to provide an inexpensive resin slide material with excellent heat resistance, mechanical properties, and flame retardancy as well as sufficient wear resistant properties; and more illustratively, to provide a polycarbonate/polyolefin based resin composition exhibiting an improved polycarbonate/-polyolefin compatibility and improved wear resistant properties as well as a molded article produced by melt molding such resin composition.
Fourth object of the present invention is to provide an inexpensive polycarbonate/polyolefin based resin composition with excellent heat resistance, mechanical properties, and flame retardancy as well as sufficient organic solvent resistance which exhibits improved polycarbonate/polyolefin compatibility; and a molded material produced by melt molding such resin composition.
Fifth object of the present invention is to provide an inexpensive glass fiber-reinforced polycarbonate/polyolefin based resin composition with excellent heat resistance, mechanical properties, and flame retardancy as well as sufficient wear resistant properties which exhibits improved polycarbonate/polyolefin compatibility; and to provide a molded article with excellent heat resistance, mechanical properties, and flame retardancy as well as sufficient wear resistant properties fabricated from such glass fiber-reinforced polycarbonate-polyolefin based resin composition.